contract extends beyond 24 months

I have been on a vodacom contract since October 1994- 21 years and counting. i have now decided to cancel my contract as i have not been given any attractive offers to stay on. my contract ends on 17 feb 2016 but vodacom cancellations insist that the only date that it can be cancelled is 29 fevruary 2016. i am asked to pay for an extra 12 days which i do not want. vodacom has had their full 24 months but still wants an extra few days. WHY WHY WHY?Vodacom lie when they say a contract is for 24 months but it is not. they try to extend as much as they can, I have tried calling everybody but nobody listens.